I. Field of the Invention
This invention relates to a novel method for the preparation of starch ether derivatives. This invention is also directed to a novel starch modifying agent and a method for its preparation.
II. Description of the Prior Art
It is well known in the art to add anionic substituent groups to starch to form anionic and amphoteric starch ester and ether devivatives. Typical of the anionic substituent groups found in starch derivatives of the prior art are carboxyalkyl groups, sulfoalkyl groups, phosphate groups, and the like. A discussion of various starch ether derivatives containing these and other anionic groups can be found in "Starch: Chemistry and Technology," Vol. 11, ed. by R. L. Whistler and E. F. Paschall (New York: Academic Press, 1967), pages 312-326. Among the reagents used to prepare carboxyalkyl starch ether derivatives are included sodium chloroacetate and salts of 1-halocarboxylic acids such as sodium 1-chloropropionate (see U.S. Pat. No. 2,523,709), sodium 1-bromopropionate, and sodium 1-bromoisovalerate (see German Patent No. 727,275). Typical reagents used to prepare sulfoalkyl starch ether derivatives are sodium haloalkyl sulfonates such as, for example, sodium 2-haloethyl sulfonates (see U.S. Pat. Nos. 2,883,375 and 2,802,000), and sodium 3-chloro-2-hydroxypropyl sulfonate (see U.S. Pat. Nos. 2,825,727 and 2,806,857).
Sulfocarboxyalkyl starch ester derivatives are also known from the prior art; e.g., U.S. Pat. No. 4,029,544 to Jarowenko et. al. teaches a pigment retention aid comprising an amphoteric starch ester derivative containing sulfosuccinate groups and cationogenic or cationic nitrogen-containing groups.
Novel starch ether derivatives containing 2-sulfo-2-carboxyalkyl ether substituents are disclosed in U.S. Pat. No. 4,199,487. In preparing these derivatives, a starch base is reacted with neutralized 3-chloro-2-sulfopropionic acid. The derivatives thus produced are useful as pigment retention aids in paper.
It is an object of the present invention to provide another economical method for preparing 2-sulfo-2-carboxyethyl starch ether derivatives.
It is a further object to provide a novel reagent for preparing starch ether derivatives and a method for the preparation thereof.